Typewriting machine



P 1931- w. F. HELMOND TYPEWRITING MACHINE Filed Jan. 14. 1929 ob M v 0 g U H Ma AM Patented Sept. 15, 1931 UNITED STATES PATENT OFFICE WILLIAM F. HELMONILOF WEST HARTFORD, CONNECTICUT, ASSIGNOR TO UNDERWOOD ELLIOTT FISHER COMPANY, OF'NEW YORK, N. Y., A. CORPORATION OF DELAWARE TYPEWRITING MACHINE Application filed January 14, 1929., Serial No. 382,433.

In typewriting machines it is desired to protect against deterioration the key-levers and the bell-cranks by which the key-levers are connected to the type-bars; and another desideratum is that the key-levers and bellcranks shall be black or dark.

It is also of importance that the touch upon the keys shall be light, and this question of touch involves the working of the joint between the key-lever and the bellcrank,-as well as of the oint between the bellcrank and the type-bar.v It is therefore desired to protect theentire key-lever and the entire bell-crank, including the joints, and to lighten the operation.

It has been the practice to use a thin metal covering for the key-lever and bell-crank, usually a metal which can be colored black. This result is gained by plating these parts with copper, and then blackening the copper. The copper plating covers the entire lever and the entire bell-crank, including the working studs or bearings which are riveted thereon. This practice has been followed for many years, but it is a feature of the present invention to piieserve the aforesaid results as to the key-lever and the bell-crank while effecting a subtsantial improvement invthe action of the keys, with a view to securin smoothness of operation, close fitting of the parts, and other advantages.

The objection to copper for plating the key-levers and bell-cranks, is that copper is a poor bearing material, and it engenders so much friction that it is highly objectionable.

-Moreover, the copper'plating must be of substantial thickness, yet it is difficult or im possible to control this thickness. Hence it is impracticable to produce at low cost, in great quantities, a finely-fitted product.

It has not been practicable to make the plating of copper very thin, because there has mulates upon the type-bars and other parts, and upon the type-bar segments, drops down onto the bell-cranks or links and rusts them, unless they are heavily plated with copper. Rust is a great enemy of the successful manufacture, shipment and sale of typewriting machines.

Other features and advantages will hereinafter appear. I

In the accompanying drawings,

Figure l is a sectional side viewof an Underwood type-action with the present invention applied thereto.

Figure 2 is an enlarged sectional view taken on the line 2-2 of Figure 1. v

Figure 3'is an enlarged sectional view taken on the line 33 of Figure 1.

According to the present invention, in order to improve the touch of the keys 10 for operating type-bars 24 to print against a platen 25, the friction-engendering copper has been eliminated from the bearings of the copper-plated lever 11 and bell-crank 12, and finished, hardened steel studs 13 are riveted to the copper-plated levers 11 and bell-cranks 12, said studs being however cadmlum-plated at 14 to protect them from rust, and also to give them lubricous surfaces conduclve to g much easier operations of the keys.

The thickness of the cadmium coatingd l' upon the stud 13 can be predetermined with great accuracy, so that the bearing will fit closely in the slot 15 or 16,in which it works, thus avoiding undue play at-the jolnt, and therefore reducing the depth of key-stroke to a minimum. Since there is considerable working of they stud along theslot at the still remain upon the head 17 M18 of the stud 13, and the head therefore will not rust, nor will rust appear between the head of the stud and the side of the lever, nor attack the bearing itself. Hence the machine is proof against injury arising from its standing for a long time upon the shelves of the factory,

or in the warehouse, or in boxes during shipment. 7

- The cadmium conduces to a light and elastic touch, and effects a substantial improvement over the old method in which the stud was copper-plated as an incident of copper-plating the entire'lever, stud and all.

Cadmium forms a hard coating and affords an exceedingly better bearing than copper, and also gives a much better protection against rust. The cadmium remains as a permanent surface on the hardened steel beariii g. It forms the best kind of surfacing for the bearing. It does no injury to the hearing itself. There is no necessity of putting on an excess of cadmium, which is a trouble which was constantly met with in coating with copper. The cadmium-coating can be made very thin and of very accurate size. The'cadmium is put on the bearings by putting the steel hearings in a tumble-barrel which is dipped in a bath of cadmium. The barrel, which is in the form of a tank, is closed up and agitated. Electric contact is made for the purpose of plating the studs with cadmium, while the barrel is revolving. The studs are plated in this way in about ten .minutes. The cadmium is self-burnishing,

and the studs are found to be brightened. There is therefore no need to r b ofi or finish the cadmium coatings on the s uds, and the cost of manufacturing the completed keylevers and bell-cranks is reduced.

The studs may be headed over or riveted I at 19 to the key-lever and bell-crank, both of which have been previously plated with copper at 20. The copper-plating extends, at 21 within the holes-22 into which the shanks 23 of the studs are inserted before heading over at 19 I i As against one ten-thousandth of an inch of cadmium plating, the thickness of the copper upon the stud has been practically'three or four thousandths. The copper-plating on the levers is subject to a great variation in thlckness, while the cadmium-plating is unithick.

-WILLIAM F. HELMOND.-

form, and the cadmium-plated stud can be made exactly the predetermined diameter and will so remain, and it is unnecessary to give attention to the questionof the thickness of the coating'or plating, as in practice it .is an insignificant matter with cadmium.

.But copper is subject to great variation in.

the thickness of the deposits. It Wlll be seen that the rusting of the joints 1s safeguarded against by the cadmium while preservlng the rust-proofing qualities of the copper-coating onthe bodies of the key-levers and bell-cranks.

Variations may be'resorted to within the scope of the invention, and portions of the improvements may be'used without others.

lilaving thus described my invention, I cla.1m1

A p voted lever having anelongated slot 

